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                <h2 id="一、魔法方法"><a href="#一、魔法方法" class="headerlink" title="一、魔法方法"></a>一、魔法方法</h2><blockquote>
<p>魔法方法总是被<strong>双下划线包围</strong>，像__init__。它<strong>总在python的适当时候被调用</strong>，是面向对象python的一切。</p>
</blockquote>
<h4 id="1-对象相关"><a href="#1-对象相关" class="headerlink" title="1.对象相关"></a>1.对象相关</h4><h6 id="init"><a href="#init" class="headerlink" title="__init__"></a>__init__</h6><ul>
<li><p>类在实例化成对象的时候会被首先调用，返回值一定为None</p>
</li>
<li><p>如果设置了其他返回值会报错</p>
<pre class="line-numbers language-none"><code class="language-none">class A:
    def __init__(self):
        return "A and A"

cup = A()<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h6 id="new"><a href="#new" class="headerlink" title="__new__"></a>__new__</h6></li>
<li><p>对象实例化时候所调用的第一个方法，很少去重写</p>
</li>
<li><p>当继承一个不可变的类型时需要重写</p>
</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none">class CapStr(str):
    def __new__(cls,string):
        string = string.upper()
        return str.__new__(cls,string)

a = CapStr("I love")
print(a)<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h6 id="del"><a href="#del" class="headerlink" title="__del__"></a>__del__</h6><ul>
<li>析构，当对象被销毁的时候调用</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none">一.类中的内置函数：
     1.__init__方法的返回值一定是None，否则会报错
     2.__new__(cls[, ...])是一个对象被实例化的时候第一个被调用的方法，
         cls参数为一个类，该方法返回的是一个对象
     3.__del__(self)：
         当对象将要被销毁时，这个方法便会被调用<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="2-算数运算"><a href="#2-算数运算" class="headerlink" title="2.算数运算"></a>2.算数运算</h4><pre class="line-numbers language-none"><code class="language-none">二.算术运算：
       1.工厂函数：其实就是一个类对象，包括 int() float() str() list() tuple()
       2.对象可以用来计算，通过其内部的魔法方法实现:
           __add__(self, onther) 定义加法的行为：+
           __sub__(self, onther) 定义减法的行为：-
           __mul__(self, onther) 定义乘法的行为：*
           __truediv__(self, onther) 定义真除法的行为：/
           __floordiv__(self, onther) 定义整除的行为：//
           __mod__(self, onther) 定义取模的行为：%
           .....
       3.反运算：在算术运算符前面多了一个'r' 如：
           __add__()就对应__radd()__
       作用：比如计算 a + b 如果a的add调用失败了，就会调用b的__radd__方法 保证计算的正确执行
       
       4.python支持增量赋值运算：
           a = a + b可以写成 a += b
       5.一元操作符：
           __neg__():表示正号的行为
           __pos__():表示负号的行为
           __abs__():表示取绝对值
           __invert__():按位取反<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<ul>
<li>示例</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none">#2.1.py
print(type(len)) #&lt;class 'builtin_function_or_method'&gt; 表示内置函数
print(type(int)) #&lt;class 'type'&gt; 表示类对象


#下面我们实现将加减法互换
#2.2.py
class New_int(int):
    def __add__(self, other):
        return int.__sub__(self, other)
    def __sub__(self, other):
        return int.__add__(self, other)
a = New_int(5)
b = New_int(6)
print(a + b)
print(a - b)

#2.3.py
class Nint(int):
    def __radd__(self, other):
        return int.__sub__(self, other)
    
a = Nint(5)
b = Nint(3)
print(a + b) # 结果为8，因为a的__add__方法被调用了
print(1 + b) # 结果为2，因为数字1没有__add__()方法，所以就执行了b的__radd__()方法

print("=====================")<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="3-属性访问"><a href="#3-属性访问" class="headerlink" title="3.属性访问"></a>3.属性访问</h4><pre class="line-numbers language-none"><code class="language-none">三.属性访问：
        类也可以通过魔法方法对其属性进行访问：
            __getattr__(self, name): 定义当用户属兔获取一个不存在的属性时的行为
            __getattribute__(self, name): 定义当该类的属性被访问时的行为
            __setattr__(self, name value): 定义一个属性被设置时的行为
            __delattr__(self, name): 定义一个属性被删除时的行为<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<ul>
<li>示例</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none">#3.1.py
class C:
    def __init__(self):
        self.x = 'X-man'
c = C()
print(c.x)
print(getattr(c, 'x', '木有这个这个属性'))
print(getattr(c, 'y', '木有这个这个属性'))

setattr(c, 'y', 'Yellow')
print(getattr(c, 'y', '木有这个属性'))
delattr(c, 'y')
#print(c.y)

print("====================")
class C:
    def __init__(self, size = 10):
        self.size = size
    def getSize(self):
        return self.size
    def setSize(self, value):
        self.size = value
    def delSize(self):
        del self.size
    x = property(getSize, setSize, delSize) #property返回size属性, x相当于size
c = C()
print(c.x)
c.x = 12
print(c.x)
del c.x #这里删除x，就相当于删除了size属性
#print(c.size)  报错

print("====================")<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="4-定制序列"><a href="#4-定制序列" class="headerlink" title="4.定制序列"></a>4.定制序列</h4><pre class="line-numbers language-none"><code class="language-none">四.定制序列
        序列类型：列表、元组、字符串，映射类型：字典，都属于容器
        定制容器：即自己定制一个容器，需要了解一些相关的协议：
        __len__(self)；调用len()方法时的行为
        __getitem__(self): 调用获取指定元素的行为
        __setitem__(self):调用设置指定元素的行为<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<ul>
<li>示例</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none">#4.1.py

class CountList:
    def __init__(self, *args):
        self.values = [x for x in args]
        self.count = {}.fromkeys(range(len(self.values)), 0)
    def __len__(self):
        return len(self.values)
    def __getitem__(self, key):
        self.count[key] += 1
        return self.values[key]
c1 = CountList(1, 3, 5, 7, 9)
c2 = CountList(2, 4, 6, 8, 10)
print(c1[1])
print(c2[1])
print(c1[1] + c2[1])
print(c1.count)
print(c2.count)

print("====================")<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="二、迭代器和生成器"><a href="#二、迭代器和生成器" class="headerlink" title="二、迭代器和生成器"></a>二、迭代器和生成器</h4><h4 id="1-迭代器"><a href="#1-迭代器" class="headerlink" title="1.迭代器"></a>1.迭代器</h4><blockquote>
<p>迭代类似于循环，每一次重复的过程称为一次<strong>迭代</strong>。提供迭代方法的容器称为<strong>迭代器</strong>，通常由序列（列表、元组、字符串）和字典。</p>
</blockquote>
<pre class="line-numbers language-none"><code class="language-none">五.迭代器
        每一次重复的过程被称为一次迭代的过程，没每一次迭代得到的
        结果会被用来作为下一次迭代的初始值
        通常接触的迭代器有：序列(列表，元组，字符串)还有字典，都支持迭代的操作
        
        对于迭代，python提供了俩个BIF：
            iter():对一个容器调用iter()就得到它的迭代器
            next()：调用next()迭代器就会返回下一个值,如果没有值了，便会抛出StopIteration异常
        迭代器的魔法方法：
            __iter()__:用于返回迭代器自身
            __next()__：决定了迭代的规则<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<pre class="line-numbers language-none"><code class="language-none">#字符串也是一个迭代器
for i in 'FishC':
    print(i)

string = 'FishC'
it = iter(string)
print(next(it))
print(next(it))
print(next(it))

class Fibs:
    def __init__(self, n = 20):
        self.a = 0
        self.b = 1
        self.n = n
    def __iter__(self):
        return self
    def __next__(self):
        self.a, self.b = self.b, self.a + self.b
        if self.a  &gt; self.n:
            raise StopIteration
        return self.a
fibs = Fibs()
for each in fibs:
    print(each)
print("====================")<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="2-生成器"><a href="#2-生成器" class="headerlink" title="2.生成器"></a>2.生成器</h4><blockquote>
<p>生成器的学习，不涉及魔法方法，而且巧妙的避开了类和对象，仅通过普通函数就可以实现，使用yield语句，这是和迭代器的区别</p>
</blockquote>
<pre class="line-numbers language-none"><code class="language-none">六.生成器与推导式
      1.生成器：生成器是迭代器的一种实现
              在普通的函数内部加上 yield 语句便构成了迭代器
              可以暂时挂起函数，并保留函数的局部变量等数据，然后在再次调用它的时候
              从上次暂停的位置继续执行下去
      2.推导式：
          有列表推导式、字典推导式、集合推导式、生成器推导式，函数参数推导式，不存在字符串推导式和元组推导式<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<pre class="line-numbers language-none"><code class="language-none">#6.1.py
#定义一个生成器，其本身是一个迭代器
def myGen():
    print("生成器被执行了")
    yield 1
    yield 2
myg = myGen()
print(next(myg))
print(next(myg))
#next(myg) 抛出StopIteration异常

#通过for循环迭代
for i in myGen():
     print(i)
print("=====================")

#6.2.py

#通过列表推导式得到能够被2整除，不能够被3整数的数
a = [i for i in range(10) if not(i % 2) and i % 3]
print(a)

#字典推导式

b = {i:i % 2 == 0 for i in range(10)}
print(b)

#集合推导式

c = {i for i in [1, 1, 2, 2, 3, 3]}
print(c)

#生成器推导式
e = (i for i in range(10) if i % 2)
for each in e:
    print(each)
#函数参数推导式

print(sum(i for i in range(100) if i % 2))<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h2 id="三、其他细节"><a href="#三、其他细节" class="headerlink" title="三、其他细节"></a>三、其他细节</h2><h4 id="1-name-’-main-’"><a href="#1-name-’-main-’" class="headerlink" title="1._name=’__main__’"></a>1._<strong>name</strong>=’__main__’</h4><blockquote>
<p>如果不适用，在导入模块使用时，会把模块中的其他<strong>需要执行的函数</strong>（非定义的函数）也执行一遍</p>
</blockquote>
<pre class="line-numbers language-none"><code class="language-none"># test.py

def test1():
    print("test1")

def test2():
    print("test2")

test2()

# user.py
import test
test.test1()

# 输出
test2
test1<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<ul>
<li>解决问题需要让python知道是作为程序运行还是导入其他程序中,需要用到模块的__name__属性</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none"># test.py

def test1():
    print("test1")

def test2():
    print("test2")

if __name__=='__main__':
    test2()
<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="2-split和join"><a href="#2-split和join" class="headerlink" title="2.split和join"></a>2.split和join</h4><pre class="line-numbers language-none"><code class="language-none">list_1 = ["qq","ww"]

#将列表转换为字符串
result = ''.join(list_1)
print(result)
#qqww

#将字符串转换为列表
result=result.split("q")
print(result)
#['', '', 'ww']
#['qqww']<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="3-python编码声明"><a href="#3-python编码声明" class="headerlink" title="3.python编码声明"></a>3.python编码声明</h4><pre class="line-numbers language-none"><code class="language-none">#coding=utf-8 

#coding:utf-8

#-*- coding:utf-8 -*-<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<blockquote>
<p>Python文件中不支持中文，中文注释也不行。为解决这个问题，就需要在代码开头声明编码格式为UTF-8。</p>
</blockquote>
<p><a target="_blank" rel="noopener" href="https://www.cnblogs.com/dplearning/p/7273209.html">参考1</a></p>
<h4 id="4-print输出格式"><a href="#4-print输出格式" class="headerlink" title="4.print输出格式"></a>4.print输出格式</h4><h6 id="命令"><a href="#命令" class="headerlink" title="命令"></a>命令</h6><p> print(对象1，对象2，sep=分割字符，end=终止符)</p>
<ul>
<li>print可以打印多个对象，用“，”分开</li>
<li>sep：规定对象的分隔符号，默认值为一个空格符（“”）</li>
<li>end：输出后自动添加的字符，默认值为换行字符（“/n”）,所以下一次命令会输出在下一行</li>
</ul>
<hr>
<h6 id="格式化输出"><a href="#格式化输出" class="headerlink" title="格式化输出"></a>格式化输出</h6><p>print(“价格为%8.2f”%price)</p>
<ul>
<li>%8.2f:表示固定输出8个字符宽度（包括小数点），保留两位小数点的浮点型</li>
<li>%d,%s,%f</li>
</ul>
<p>print(“%s  %d”%(name,age))</p>
<hr>
<h6 id="不换行与换行输出"><a href="#不换行与换行输出" class="headerlink" title="不换行与换行输出"></a>不换行与换行输出</h6><p>   # 换行输出</p>
<p>   print(x)   </p>
<p>   # 不换行输出</p>
<p>   print(x,end=’’)</p>
<h4 id="5-format-输出格式"><a href="#5-format-输出格式" class="headerlink" title="5.format 输出格式"></a>5.format 输出格式</h4><table>
<thead>
<tr>
<th>数字</th>
<th>格式</th>
<th>输出</th>
<th>描述</th>
</tr>
</thead>
<tbody><tr>
<td>3.1415926</td>
<td>{:.2f}</td>
<td>3.14</td>
<td>保留小数点后两位</td>
</tr>
<tr>
<td>3.1415926</td>
<td>{:+.2f}</td>
<td>+3.14</td>
<td>带符号保留小数点后两位</td>
</tr>
<tr>
<td>-1</td>
<td>{:+.2f}</td>
<td>-1.00</td>
<td>带符号保留小数点后两位</td>
</tr>
<tr>
<td>2.71828</td>
<td>{:.0f}</td>
<td>3</td>
<td>不带小数</td>
</tr>
<tr>
<td>5</td>
<td>{:0&gt;2d}</td>
<td>05</td>
<td>数字补零 (填充左边, 宽度为2)</td>
</tr>
<tr>
<td>5</td>
<td>{:x&lt;4d}</td>
<td>5xxx</td>
<td>数字补x (填充右边, 宽度为4)</td>
</tr>
<tr>
<td>10</td>
<td>{:x&lt;4d}</td>
<td>10xx</td>
<td>数字补x (填充右边, 宽度为4)</td>
</tr>
<tr>
<td>1000000</td>
<td>{:,}</td>
<td>1,000,000</td>
<td>以逗号分隔的数字格式</td>
</tr>
<tr>
<td>0.25</td>
<td>{:.2%}</td>
<td>25.00%</td>
<td>百分比格式</td>
</tr>
<tr>
<td>1000000000</td>
<td>{:.2e}</td>
<td>1.00e+09</td>
<td>指数记法</td>
</tr>
<tr>
<td>13</td>
<td>{:&gt;10d}</td>
<td>13</td>
<td>右对齐 (默认, 宽度为10)</td>
</tr>
<tr>
<td>13</td>
<td>{:&lt;10d}</td>
<td>13</td>
<td>左对齐 (宽度为10)</td>
</tr>
<tr>
<td>13</td>
<td>{:^10d}</td>
<td>13</td>
<td>中间对齐 (宽度为10)</td>
</tr>
<tr>
<td>11</td>
<td><code>'{:b}'.format(11) '{:d}'.format(11)'{:o}'.format(11) '{:x}'.format(11) '{:#x}'.format(11) '{:#X}'.format(11)</code></td>
<td><code>1011 11 13 b 0xb 0XB</code></td>
<td>进制</td>
</tr>
</tbody></table>
<pre class="line-numbers language-none"><code class="language-none">'''
1、使用位置参数
要点：从以下例子可以看出位置参数不受顺序约束，且可以为{},
只要format里有相对应的参数值即可,参数索引从0开，
传入位置参数列表可用*列表
'''
li = ['hoho',18]
print('my name is {} ,age {}'.format('hoho',18))
print('my name is {1} ,age {0}'.format(10,'hoho'))
print('my name is {1} ,age {0} {1}'.format(10,'hoho'))
print('my name is {} ,age {}'.format(*li))#打包
# my name is hoho ,age 18
# my name is hoho ,age 10
# my name is hoho ,age 10 hoho
# my name is hoho ,age 18

'''
2、使用关键字参数
要点：关键字参数值要对得上，可用字典当关键字参数传入值，
字典前加**即可
'''
hash = {'name': 'hoho', 'age': 18}
print('my name is {name},age is {age}'.format(name='hoho',age=19))
print('my name is {name},age is {age}'.format(**hash))
# my name is hoho,age is 19
# my name is hoho,age is 18

'''
3、填充与格式化
:[填充字符][对齐方式 &lt;^&gt;][宽度]

&gt;&gt;&gt; '{0:*&gt;10}'.format(10)  ##右对齐
'********10'
&gt;&gt;&gt; '{0:*&lt;10}'.format(10)  ##左对齐
'10********'
&gt;&gt;&gt; '{0:*^10}'.format(10)  ##居中对齐
'****10****'

 
4、精度与进制

&gt;&gt;&gt; '{0:.2f}'.format(1/3)
'0.33'
&gt;&gt;&gt; '{0:b}'.format(10)    #二进制
'1010'
&gt;&gt;&gt; '{0:o}'.format(10)     #八进制
'12'
&gt;&gt;&gt; '{0:x}'.format(10)     #16进制
'a'
&gt;&gt;&gt; '{:,}'.format(12369132698)  #千分位格式化
'12,369,132,698'

 
5、使用索引
&gt;&gt;&gt; li
['hoho', 18]
&gt;&gt;&gt; 'name is {0[0]} age is {0[1]}'.format(li)
'name is hoho age is 18
'''
<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h4 id="6-input命令"><a href="#6-input命令" class="headerlink" title="6.input命令"></a>6.input命令</h4><blockquote>
<p>变量 = input（提示字符串）</p>
</blockquote>
<h4 id="7-open"><a href="#7-open" class="headerlink" title="7.open()"></a>7.open()</h4><p>Python open() 函数用于打开一个文件，并返回文件对象，在对文件进行处理过程都需要使用到这个函数，如果该文件无法被打开，会抛出 OSError。</p>
<pre class="line-numbers language-none"><code class="language-none">open(file, mode='r')
open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)
file: 必需，文件路径（相对或者绝对路径）。
mode: 可选，文件打开模式
buffering: 设置缓冲
encoding: 一般使用utf8
errors: 报错级别
newline: 区分换行符
closefd: 传入的file参数类型
opener:<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<p>mode 参数有：</p>
<table>
<thead>
<tr>
<th>模式</th>
<th>描述</th>
</tr>
</thead>
<tbody><tr>
<td>t</td>
<td>文本模式 (默认)。</td>
</tr>
<tr>
<td>x</td>
<td>写模式，新建一个文件，如果该文件已存在则会报错。</td>
</tr>
<tr>
<td>b</td>
<td>二进制模式。</td>
</tr>
<tr>
<td>+</td>
<td>打开一个文件进行更新(可读可写)。</td>
</tr>
<tr>
<td>U</td>
<td>通用换行模式（不推荐）。</td>
</tr>
<tr>
<td>r</td>
<td>以只读方式打开文件。文件的指针将会放在文件的开头。这是默认模式。</td>
</tr>
<tr>
<td>rb</td>
<td>以二进制格式打开一个文件用于只读。文件指针将会放在文件的开头。这是默认模式。一般用于非文本文件如图片等。</td>
</tr>
<tr>
<td>r+</td>
<td>打开一个文件用于读写。文件指针将会放在文件的开头。</td>
</tr>
<tr>
<td>rb+</td>
<td>以二进制格式打开一个文件用于读写。文件指针将会放在文件的开头。一般用于非文本文件如图片等。</td>
</tr>
<tr>
<td>w</td>
<td>打开一个文件只用于写入。如果该文件已存在则打开文件，并从开头开始编辑，即原有内容会被删除。如果该文件不存在，创建新文件。</td>
</tr>
<tr>
<td>wb</td>
<td>以二进制格式打开一个文件只用于写入。如果该文件已存在则打开文件，并从开头开始编辑，即原有内容会被删除。如果该文件不存在，创建新文件。一般用于非文本文件如图片等。</td>
</tr>
<tr>
<td>w+</td>
<td>打开一个文件用于读写。如果该文件已存在则打开文件，并从开头开始编辑，即原有内容会被删除。如果该文件不存在，创建新文件。</td>
</tr>
<tr>
<td>wb+</td>
<td>以二进制格式打开一个文件用于读写。如果该文件已存在则打开文件，并从开头开始编辑，即原有内容会被删除。如果该文件不存在，创建新文件。一般用于非文本文件如图片等。</td>
</tr>
<tr>
<td>a</td>
<td>打开一个文件用于追加。如果该文件已存在，文件指针将会放在文件的结尾。也就是说，新的内容将会被写入到已有内容之后。如果该文件不存在，创建新文件进行写入。</td>
</tr>
<tr>
<td>ab</td>
<td>以二进制格式打开一个文件用于追加。如果该文件已存在，文件指针将会放在文件的结尾。也就是说，新的内容将会被写入到已有内容之后。如果该文件不存在，创建新文件进行写入。</td>
</tr>
<tr>
<td>a+</td>
<td>打开一个文件用于读写。如果该文件已存在，文件指针将会放在文件的结尾。文件打开时会是追加模式。如果该文件不存在，创建新文件用于读写。</td>
</tr>
<tr>
<td>ab+</td>
<td>以二进制格式打开一个文件用于追加。如果该文件已存在，文件指针将会放在文件的结尾。如果该文件不存在，创建新文件用于读写。</td>
</tr>
</tbody></table>
<p>默认为文本模式，如果要以二进制模式打开，加上 b 。</p>
<h4 id="8-with语句"><a href="#8-with语句" class="headerlink" title="8.with语句"></a>8.with语句</h4><ul>
<li>用于打开文件时不用关闭文件</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none">with open(r'c:\test.txt', 'r') as f:
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